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| Home > Publications database > Carbonyl Sulfide in the Stratosphere: airborne instrument development and satellite based data analysis |
| Book/Dissertation / PhD Thesis | FZJ-2017-08315 |
2017
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
ISBN: 978-3-95806-276-4
Please use a persistent id in citations: http://hdl.handle.net/2128/16295
Abstract: Carbonyl sulfide plays a crucial role in the global atmospheric sulfur cycle and therefore for the global climate. It is the most abundant sulfur containing gas in the atmosphere during volcanic quiescence and is converted to aerosol in the stratosphere, which has a cooling effect on the climate. This work contributes to a better understanding of the role of $\textbf{OCS}$ in the upper troposphere and lower stratosphere. Satellite based data were analyzed and a new instrument AMICA (Airborne Mid-Infrared Cavity enhanced Absorption spectrometer) for in-situ $\textbf{OCS}$ measurements on stratospheric research aircraft was developed. $\textbf{OCS}$ data set from the satellite based instrument ACE-FTS, the stratospheric $\textbf{OCS}$ burden was calculated to be 524 Gg, which is 10 % of the total atmospheric $\textbf{OCS}$ budget and is in agreement with a sulfur cycle model. No trend in the global burden is observed between 2004 and 2016. Due to the sparse spacial coverage of the data set of ACE-FTS, a sampling bias arises when computing climatological averages over seasons and latitude bands. This sampling bias is corrected for with a newly developed procedure, using a mathematical interpolation. To estimate the significance and magnitude of the bias for each data point, the performance of the interpolation method was tested and some limitations identified. Additionally, with the ACE-FTS data set, a significant increase in $\textbf{OCS}$ ($\textbf{CO}$ and $\textbf{HCN}$) mixing ratios is observed in the Asian monsoon anticyclone, a pathway from the highest polluted region on earth into the stratosphere. An analysis of the $\textbf{HCN:OCS}$ ratios supports the suggestion of a transport from the Bay of Bengal region outside to the southern border of the anticyclone with air masses in the Asian monsoon anticyclone mostly originating from continental convection. The Asian monsoon and the features seen with the ACE-FTS data set will be investigated in detail with the new in-situ, high resolution instrument AMICA during the EU-project StratoClim. AMICA has been developed and tested as part of this thesis. Important tests were made that contributed to the mechanical design and measurement set up in the final AMICA instrument. Key components include a box-shaped pressure tight enclosure, a flow system that regulates the cavity pressure over a wide ambient pressure range, spanning the full altitude range of available research aircraft, and the establishment of an $\textbf{OCS}$ calibration system. AMICA successfully measured $\textbf{OCS}$ as well as $\textbf{CO}$, H$_{2}$ and H$_{2}$$\textbf{O}$ during its first campaign that comprised three flights from Kalamata, Greece in summer 2016. $\textbf{OCS}$ measurements show decreasing mixing ratios in the stratosphere as expected and a larger variability in the UTLS region than expected. The complete data set of the important tropospheric tracer $\textbf{CO}$ was provided to the StratoClim community. A comparison with a nearby ACE-FTS profile shows a reasonably good agreement between AMICA and ACE-FTS in the stratosphere. Further measurement flights in the UTLS region will help understand the detected higher variability of $\textbf{OCS}$ in the UTLS. This can improve the representation of $\textbf{OCS}$ in global climate models.
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